He led the Montreal Alouettes of the Canadian Football League (CFL) to back-to-back Grey Cup victories in 2009 and 2010, and another as head coach of the Toronto Argonauts in 2017.

[8] That year, quarterback Bernie Kosar passed for 2,329 yards and Miami won the national championship.

In 2005, Trestman returned to college football coaching as the NC State Wolfpack offensive coordinator, guiding the team to a win in the Meineke Car Care Bowl.

[10] Trestman moved to the National Football League and coached running backs with the Minnesota Vikings in 1985 and 1986.

His promotion to offensive coordinator in 1989 was made before the team named Bud Carson as Marty Schottenheimer's successor as head coach.

Trestman was dismissed after the Browns' third loss in the AFC Championship game in four years, primarily due to his strained relationship with Carson.

[10] He returned to the NFL in 1995 as quarterbacks coach and offensive coordinator with San Francisco, where he served in that capacity through 1996.

That year Lions quarterback Scott Mitchell passed for 3,484 yards, fourth most in team history.

At the conclusion of the season, he was nominated for the CFL's Annis Stukus Award as the league's top coach, with Calgary's John Hufnagel winning.

Under Trestman's guidance, Alouettes QB Anthony Calvillo won back-to-back MVP awards in 2008 and 2009.

[14] In early 2013, Trestman was interviewed by the Chicago Bears[15] and the Cleveland Browns for their respective vacant head coaching positions.

Despite this, Trestman spoke with confidence that he would be back as the Bears' head coach next season following a 13–9 loss to the Minnesota Vikings.

[25] Trestman issued a final statement before leaving: "I want to thank Virginia, George and the McCaskey family, Phil Emery and Ted Phillips for giving me the opportunity to be the head coach of the Chicago Bears.

Trestman inherited a roster that finished last in the league the previous season, and guided the team to a 9–9 record, which was good enough for first place in the East and a first-round bye in the playoffs.

The 2018 season for the Argonauts under Trestman was filled with poor play and injuries (most notably to quarterback Ricky Ray) resulting in the team missing the post-season following the Grey Cup Championship the year before.

[29] On February 14, 2024, Trestman was hired by Jim Harbaugh to join the Los Angeles Chargers as a senior offensive assistant.

"[32] He also co-hosted The Leadership Gameplan Podcast on behalf of the University of Miami School of Law with Greg Levy.

[33] Trestman is a "Football Player Development" instructor for the online sports-career training school Sports Management Worldwide.